Yes, IDT can synthesize oligonucleotides for customers using trimer phosphoroamidites.
You can order Trimer 19 using modification code /iTriMix19/, or Trimer 20 using modification code /iTriMix20/,
To order a Custom Trimer Mix, email email@example.com with your name, organization, and sequence designs. Oligos containing Custom Trimer Mixes can be ordered with standard desalt (recommended for oligos containing mixes), provided that other modifications included in the sequence do not require HPLC.
For more information about trimer mixes, see the article, Generate codon balanced libraries for mutagenesis with trimer modifications, or contact firstname.lastname@example.org.